Shear reactor for vortex synthesis of nanotubes

ABSTRACT

Continuous nanotube synthesis by vortex deposition occurs in an axially-fed shear reactor comprising coaxial counter-rotating disk impeller/electrodes charged as anodes. Nanotube evolving ends, charged as cathodes, point toward the anode axis of rotation and protrude into the space between the anodes. Radial vortices in a shear layer of the space, between the boundary layers on the impeller/electrodes, spin cations to be deposited on evolving nanotube ends approximately at the vortex axis, so deposition is by swirling cathode fall. The evolved nanotubes are extracted mechanically, and they conduct electrons from charging means to charge the evolving ends as cathodes. The preferential synthesis of metallic carbon nanotubes is due to the greater resistance of non-metallic structures such as graphite or semiconductive structures. Ozone serves to oxidize non-metallic structures and to functionalize the loose ends of nanotube fragments. Dopants can be added to the evolving nanotubes by introduction of dopants at the periphery because the evolving ends are maintained in stable locations. Or dopants can be added by the simultaneous decomposition of gases (for example, carbon dioxide and nitrogen gas) within the reactor or in an external reactor.

APPLICATION HISTORY

The applicants claim the benefit of provisional application 61/026,963entitled “Continuous Synthesis of Carbon Nanotubes by Vortex Turbulence”filed Feb. 7, 2008 by Wilmot H. McCutchen and David J. McCutchen, aswell as provisional application 61/034,242 entitled “Dual Disk DynamoHigh Shear Reactor” by Wilmot H. McCutchen and David J. McCutchen, filedMar. 6, 2008.

FIELD OF THE INVENTION

This invention applies to the synthesis of carbon or other nanotubes andto electrolysis in turbulent reactors.

BACKGROUND OF THE INVENTION

Nanotubes have been synthesized from many materials, including boronnitride, tungsten disulfide, titanium dioxide, molybdenum disulfide,bismuth, copper, and gold.

Carbon nanotubes in particular are a commercially valuable form ofcarbon that has many remarkable properties. The fibers are 100 timesstronger in tensile strength than steel, and are the most efficient heatconductors known. These nanotubes have a high degree of stiffness, dueto their molecular structure. They can theoretically be formed in anylength, but present methods of formation include a random direction offormation, and this limits the resulting length the nanotube to a coupleof centimeters as best.

Chemical vapor deposition is a method currently used by commercialcompanies creating quantities of nanotubes. The formation of thenanotubes is made from the evaporation of a solution of carbon or otherions suspended in alcohol or another solvent. This makes the tubes formin random directions to a length of at most a few millimeters. Thesolvent with the forming tubes can be in the form of an aerogel, and thefinal step of deposition can be as the aerogel is being drawn into acable. This can achieve speeds of deposition of up to 2 meters a minute,but the cable is a grouping of short nanotube lengths, and lacks thetensile strength that would come from a single long nanotube.

Laser ablation and arc discharge are other synthesis methods. In laserablation for carbon nanotubes, a high energy laser vaporizes acarbonaceous target to produces carbon ions, whereas arc dischargevaporizes carbon electrodes. Isotropic turbulence spins some of thesecarbon ions into nanotubes, which are very short in length due to thechaotic orientation and short duration of any formation vortices.

Depending on their structure, carbon nanotubes can be electricalsuperconductors, also known as metallic nanotubes, or semiconductors.Conventional synthesis methods produce a mixture of conductive andsemiconductor nanotubes, which must later be separated by suitable meansoutside of the reactor.

SUMMARY AND OBJECTS AND ADVANTAGES OF THE PRESENT INVENTION

The present invention represents a scalable approach to continuoussynthesis of long nanotubes. A flow of carbon ions is organized intoradial vortices which feed the formation of continuously evolvingnanotubes. The ion vortices are mechanically forced by counter-rotatingdisk impeller/electrodes, and the vortices create a solenoidal magneticfield which causes self-tightening of the vortex. Turbulence isanisotropic, or directionally oriented, instead of the random isotropicturbulence of conventional reactors, so the vortices are coherent andradially arranged. The formation process within these vortices favorsthe creation of longer strands that can be spooled up to an externalreel continuously. This can make the production of long nanotube strandsin large quantities a commercial reality.

Another advantage is that the formation process tends to favor theproduction of metallic instead of semiconducting nanotubes. The evolvingnanotubes are charged as cathodes, and the current will flow easilythrough the metallic nanotubes to their evolving ends, but does not floweasily through semiconductive nanotubes due to their higher resistance.Therefore semiconductive nanotubes tend not to evolve because theirevolving ends are starved of electrons by their resistance.

A further advantage is the production of doped nanotubes with variationsalong their length, produced by changing the conditions in which theevolving end of the nanotube is formed.

The ion source may be electrolysis within the shear reactor, or anexternal source. In the case of an external source, the source gas fedinto the shear reactor is a mixture of a carrier gas and the ions whichwill be rolled into nanotubes by coherent directed turbulence andswirling cathode fall. The nanotubes could therefore be of gold or otherconventional nanotube materials, as well as of carbon.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of one half of the preferred embodiment of thevortex synthesis shear reactor of the present invention.

FIG. 2 is a cross section close-up of the area of the formation zone.

FIG. 3 is a front view of the peripheral wall, seen from the space inthe reactor.

FIG. 4 is a top view of the reactor, showing the array of radialvortices.

FIG. 5 is a cross section of one half of an alternative embodiment,comprising converging anodes.

LISTED PARTS

-   2. Top disk impeller/electrode-   4. Bottom disk impeller/electrode-   5. Peripheral wall-   6. Source gas-   7. Space-   8. Axial source gas vent-   9. Support spindle-   10. Axis of rotation of the disk impeller/electrodes 2,4-   12. Charging means-   14. Carbon ions-   16. Hole in sintered metal anode-   17. Exhaust port-   18. Radial vortex-   20. Curved vortex reflector-   21. Pressure vent in reflector surface-   22. Conical protrusion-   24. Evolving end of nanotube-   26. Central opening in conical protrusion 22-   28. Ozone feed-   30. Electrons from cathode-   32. Carbon ion outer vortex-   34. Withdrawal of nanotube-   36. Formation zone-   38. Rebound vortex-   40. Dopant source-   42. Control for dopant source-   44. Dopant ion-   46. Dopant ion in nanotube structure-   48. Dopant exhaust vent-   50. Dopant exhaust-   52. Reflector vent negative pressure-   54. Reflector vent positive pressure-   56. Nanotube cable-   58. Takeup reel-   60. Seal between peripheral wall and disk impeller-   62. Disk pinch section-   64. Slit opening-   66. Ozone chamber-   68. Nanotube yarn-   70. Precision extraction means

DETAILED DESCRIPTION

The following description is directed toward the production of carbonnanotubes, but the present invention can be used to synthesize nanotubesand other tubular fullerene structures from other suitable compounds.

Controlled turbulence is used in a shear reactor to create coherentradial vortices of carbon ions in a shear layer between counter-rotatingand coaxial disk anodes. Residence time of ions in the reactor is long,and the ion vortices deposit ions in swirling cathode fall on evolvingnanotube ends during this residence time. The nanotubes are thenwithdrawn from the reactor.

Carbon or other metal ions (cations) concentrate in the shear layerbecause they are repelled from the anodes. Because of thecounter-rotation of the disk impeller/electrodes, the radial vortices 18in the shear layer are radially oriented like spokes of a wheel withrespect to the disk axis of rotation 10. Each vortex contains aformation zone at its core where carbon ions are concentrated at thepoint of formation of an evolving nanotube. Each nanotube has a captiveend and an evolving end. The evolving end is charged as a cathode andgrows as more carbon ions aggregate to it to form the characteristicpattern of connections of a nanotube. The captive end is used to pullthe nanotube out from the periphery of the reactor continuously toprevent the evolving end from leaving the formation zone, and thecaptive end is a conductor of electrons to the evolving end. To improvethe quality and functionalize the nanotubes, they preferably should beexposed to ozone as they leave the formation zone and are withdrawn fromthe reactor.

As shown in the schematic cross sectional view of one half of the shearreactor in FIG. 1, the controlled turbulence vortex is forced by twoapproximately parallel and coaxial counter-rotating diskimpeller/electrodes 2 and 4 which act as centrifugal impellers of asource gas 6 axially injected to the space 7 between them. The topimpeller 2 rotates into the page, and the bottom impeller 4 rotates outof the page. Their common axis of rotation 10 is approximately at thecenterline of the reactor.

By the term counter-rotating is meant simultaneous rotation other thanexactly co-rotating, as for example, where both impeller/electrodesrotate in the same direction but at different angular velocities, orwhere one rotates and the other is static. Preferably, there is exactcounter-rotation, where the opposed coaxial impeller/electrodes 2,4rotate in opposite directions at approximately the same angularvelocity. Suitable means, not shown, connected to theimpeller/electrodes cause them to counter-rotate.

The counter-rotating disk electrode/impellers 2,4 in combination with aperipheral wall 5 define a space 7 where vortex synthesis of nanotubesis forced. Axial feed of a source gas 6 to the space 7 between theimpellers 2,4 is caused by positive pressure through axial source gasvents 8 in a cylindrical support spindle 9 which supports the impellers2,4 and maintains them in a coaxial orientation around their common diskaxis of rotation 10.

The support spindle is connected to external charging means 12 and actsas a conductor between the charging means and the impellers, making thespindle and each impeller/electrode 2,4 an anode. The external chargingmeans 12 for the anodes are coupled to the static support spindle, andthrough its seals to the disks, with the seals being mercury seals orother electrically conductive seals. Alternatively, the disks, spindleand peripheral wall can all be charged as anodes separately. Thecharging means provides constant or pulsed sonic or radio frequencydirect current. A conventional current (positive ions) flows into theevolving end as an electron current flows out of it. Intermittentcurrent would serve to soften the impact of the ions on the nanotubeend.

A source gas is 14 is axially fed into the space between the anodes. Theterm source gas includes a plasma created in an external reactor.Preferably the source gas comprises ions produced by an external source.The source gas may comprise cations mixed with and an inert carrier gassuch nitrogen, argon or xenon.

Alternatively, the source gas could be a carbonaceous gas such as carbonmonoxide which has not yet been ionized. The source gas may comprisecarbonaceous molecules such as methane (CH₄), acetylene (C₂H₂), carbonmonoxide (CO) or carbon dioxide (CO₂). It may also comprise molecules ofa volatile organic compound (VOC). The source gas may include sulfurdioxide. What will be described below is a shear reactor for theelectrolytic decomposition of carbon monoxide to form metallic carbonnanotubes.

The carbon ions can be produced in the reactor by the decomposition of acarbonaceous source gas, preferably carbon monoxide because it isabundant and because dissociation produces carbon and ozone. Ozonesurrounding the nanotubes serves to functionalize loose ends and tooxidize non-nanotube structures which would clutter the product of thereactor.

The source gas, whether an externally created plasma or a gas to bedissociated by electrolysis within the reactor, is injected through atleast one axial source gas vent 8 and is advected radially outward fromthe disk axis of rotation in boundary layers against the anodes. Theanodes repel cations, such as carbon ions, into a shear layer betweenthe boundary layers.

Evolving nanotube ends 24, which are charged as cathodes, extend intothe shear layer. Arcing between the anodes 2,4 and cathodes 24 isprevented by the continuous rotation of the anodes, breaking incipientarcs and causing a diffuse, or corona, discharge in the space 7.Therefore a high amount of energy can be pumped into the space 7 todecompose the source gas. Not only electrical energy but also mechanicalenergy is transferred to the source gas by the high shear of thereactor.

If the source gas is carbon monoxide (CO), the bond dissociation energyis 9.144 eV. Because the shear reactor of the present invention has highresidence time, there is time to pump the required dissociation energyinto the space 7 between the disk impeller/electrodes 2,4. High pressurein the space 7 is caused by positive feed pressure through the axialfeed gas vents 8 and the added enthalpy due to the work of the rotatingimpeller/electrodes on the source gas.

Decomposition of the carbonaceous source gas creates a cloud of carbonions 14 in the shear layer between the impeller/electrodes, while oxygenor other electrolysis product gases are evolved at the anode impellersurfaces. Preferably the impellers are of sintered metal so as topresent a large surface area to the source gas and to provide many holes16 for the exit of electrolysis product gases.

In the case of a source gas comprising cations mixed with a carrier gas,such as nitrogen, argon, or xenon, the cations are repelled by theanodes and the carrier gas flows through boundary layers against theimpeller/electrodes and out of the reactor through the holes 16 in theanodes and through exhaust ports 17 in the periphery 5. Some of theoxygen gas becomes ozone, which because it has a heavier molecularweight than the source gas flows radially outward to the peripheral wall5.

The shear layer comprises a multi-scale network of radial vortices. Atthe periphery of the reactor, the radius of the radial vortices issmall. The turbulence within the reactor is organized and anisotropicdue to the forcing of the counter-rotating disk impeller/electrodes 2,4and the continuous mass flow in and out of the reactor. The axes of theradial vortices 18 are approximately orthogonal to the disk axis ofrotation 10.

Impingement of the vortex end on the peripheral wall 5 causescontraction of the radial vortex 18 due to the mechanics of thevortex-wall interaction. A resultant rebound directed away from theperipheral wall along the vortex axis of rotation pulls the evolving end24 of the nanotube back toward the disk axis of rotation 10 in a tighterrebound vortex 38.

Within this small radius rebound vortex 38 is a concentrated rapid swirlof cations, which by their vortex motion create a solenoidal magneticfield that causes the cation vortex to self-tighten into an even smallerradius. At the core of the vortex is a region with the optimalconditions for nanotube assembly, called the formation zone. Theevolving end 24, charged as a cathode dangles in the formation zone, andcations deposit on the evolving end continuously in swirling cathodefall.

The rotation of carbon ions in a radial vortex in the shear layerproduces a solenoidal magnetic field, because charges in motion alwaysproduce a magnetic field. Here we have positive charges in coherentvortex motion, which, according to the right hand rule, will produce asolenoidal magnetic field having a North pole pointing at the peripheralwall 5. Carbon ions rotating through this mechanically forced magneticfield experience a magnetic force squeezing them into the vortex axis.The self-tightening of the carbon ion vortices due to mechanicallyforced anisotropic turbulence also acts to knit the carbon ions into ananotube structure.

As the nanotube lengthens toward the disk axis of rotation 10,extraction means such as a takeup reel 58 pull the evolving end backtoward the peripheral wall and thus maintain the evolving end in theformation zone at an optimal distance from the peripheral wall. Chargingmeans 12 connected to the takeup reel 58 charge it as a cathode, andnanotubes pulled by it conduct electrons to the formation zone.Metallic, or conductive, nanotube structures are favored in formationbecause they conduct electrons with less resistance than semiconductivenanotube structures. Therefore the nanotube evolving ends 24 dangling inthe formation zone will preferentially be ends of metallic carbonnanotubes.

Tension in the nanotube due to the pull of the takeup reel 58 versus theforce of the rebound from the vortex-wall interaction acts to stretchand anneal the nanotube and provides means for maintaining the evolvingend in the formation zone.

The optimal withdrawal speed for the evolving end is determined by themonitoring or conditions inside the reactor such as feed pressure,temperature, charge and ion density. It may also be determined by ameasurement of the piezoelectric activity of the nanotube as it flexesin the swirl of the vortex or remains calm in the vortex core. Suitablemeans known to the art, such as stepper motors and gearing for precisionmovement, may connect to the takeup reel 58 and the nanotube cable 56itself and control its speed, both into and out of the shear reactor, soas to maintain the evolving end 24 at an optimal location in the space7. Experiment using constant reactor conditions could also determine anoptimal constant takeup reel speed. The withdrawal means closest to thereactor should preferably include precision extraction means forgripping and advancing a nanotube in a linear motion as needed.

Preferably the peripheral wall 5 comprises one or more concave cavitiesfacing the space 7. Each cavity is a curved vortex reflector 20 to focusand tighten the rebound vortex to make a tighter concentration or carbonions. At the center of the vortex reflector 20, is an approximatelyconical protrusion 22, comprising a central opening 26 for the cathodeto extend into the space 7. Preferably, the peripheral wall 5 should becharged as an anode, to prevent carbon coking, but the vortex reflector20 should be dielectric, to prevent arcing between the cathode evolvingend 24 and the anode peripheral wall 5.

Alternatively, the peripheral wall could be without vortex reflectors orconical protrusions but having one or more holes through it.Alternatively, the peripheral wall could be not static, but part of theimpellers, with half of the peripheral wall on each impeller, as in thealternative embodiment comprising converging anodes, as shown in FIG. 5.

Vapor source gas could be ionized by arc discharge between the evolvingnanotube ends and the counter-rotating anodes. The arc discharge wouldbe a corona because arc dwelling on the anodes is broken continuously byrotation of the anode arc site away from the cathode. Shear plus coronadischarge pumps sufficient energy into the vapor for ionization. Thevapor could be of an organic compound, of metals, of carbon, or of othercation sources.

Carbonaceous source gas could provide cations for carbon nanotubesynthesis by dissociation within the shear reactor according to thepresent invention. The evolving nanotube ends are cathodes, and the diskimpeller/electrodes are anodes. Discharges in the space are in thenature of corona discharges rather than dwelling arcs because therotation of the anodes breaks incipient arcs and prevents them fromdwelling. For example, carbon monoxide, is decomposed in the reactor,providing carbon cations for nanotube deposition and oxygen for ozone.

Von Karman swirling flow in an open system occurs in the space 7 of ashear reactor according to the present invention because there is highshear between counter-rotating coaxial disk impeller/electrodes 2,4 andthere is simultaneous and continuous mass flow in (through the axialsource flow vents 8) and out (through the impeller holes 16 and theexhaust ports 17). The flow is not disordered, as in closed systemsetups, but comprises a multiscale array of branched radial vortices dueto the fact that this is an open system. Radial counterflow is forced inthe space 7 by counter-rotation of the disk impeller/electrodes 2,4.Against each disk impeller/electrode is a boundary layer. Source gas andgaseous electrolysis products, such as ozone, flow radially outward fromthe axis of rotation 10. Radially inward flow toward the axis 10 occursin the shear layer between the counter-rotating boundary layers.Recirculating flow radially inward through the shear layer toward theimpeller axis of rotation is caused by the rebound resulting from thevortex-wall interaction as vortices in the shear layer encounter theperiphery wall 5 enclosing the space 7 between the impellers.

As shown in the schematic cross section of the area of the formationzone in FIG. 2, at the center of each curved reflector 20 for a shearlayer carbon ion vortex 32, a protruding central cone 22 extends intothe axis of the tightened rebound vortex 38. The evolving end 24 of thenanotube extends from a small opening 26 in the tip of this cone andradially inward toward the disk axis. Here the opening is shown largerfor purposes of clarity; the opening 26 for the nanotube should benarrow to allow better control of the positioning of the nanotubeevolving end 24. In the vicinity of the evolving end 24 is a formationzone 36 including the core of the carbon ion rebound vortex 38. Theformation zone in the vortex core is a space of relative calm having adense and evenly distributed concentration of carbon ions orbiting inclose proximity to the evolving end 24, which favors balanced and rapidgrowth. Preferably, the opening 26 comprises insulating material so asto prevent the nanotube evolving end 24 from shorting. For example, theconical protrusions could be of ceramic insulating material.

Unlike the counter-rotating disk impeller/electrodes 2,4, which arecharged as anodes, the evolving nanotube tip is charged as a cathode bycharging means 12. The charging means 12 connect to the takeup reel 58and the nanotubes conduct electrons to the evolving ends. Nanotubes areknown to be very efficient field emitters of electrons, due to thesharpness of their points. The carbon ion vortices have an electrondeficiency. The cathode source of electrons 30 attracts the carbon ions14 in a dense cloud around the evolving end 24, continuously drawing incarbon ions in swirling cathode fall for continuous vortex deposition,allowing the synthesis of very long nanotubes. As the length of thenanotube grows, it is withdrawn 34 back through the cone, to prevent theevolving end 24 from leaving the formation zone 36.

Any ozone (O₃) resulting from electrolysis functionalizes the ends ofnanotube fragments and any sites of defective formation, which is wherenanotubes are vulnerable to oxidation. If ozone is not present fromelectrolysis, it should be supplied in an ozone feed 28 outside theperipheral wall, which bathes the emerging nanotube and extends throughthe opening 26 toward the formation zone. Graphitic or coke solid carbonis oxidized by the ozone and recycled in the reactor, so theseimpurities are minimized in the solid carbon structures produced by thepresent invention. Semiconductive and nonconductive damaged nanotubesare also excluded from production because their evolving ends arestarved of electrons due to their high resistance, whereas metallicnanotubes, which are excellent conductors, are better able to suck theelectrons from the charging means to augment their evolving ends.

Nanotube cables 56 are grown from a captive stub extending into theformation zone. For starting the growth process, the nanotube stub canbe short, and attached if necessary to a wire that attaches to thetakeup reel or other withdrawal means and extends the stub into theformation zone. Nanotube stubs could be metal wires connected to thetakeup reel 58 and extending into the space 7. On startup of thereactor, carbon nanotubes begin to deposit on the end of the wire, andthe wire is drawn out of the space 7 along with the nanotubes attachedto it. The type of nanotube stub can influence the type of growthproduced, since the growth will tend to duplicate the structureavailable. The stub can be single wall, multiwall or multistrand. Ifseveral nanotube ends are presented together as a stub, then amultistrand cable will be the result.

A charged cathode wire can also attract nanotube growth in the form of atangle of shorter nanotubes, which in turn are charged as a cathode toencourage further growth. This nanotube “yarn” can also be formed andwithdrawn continuously. Loose ends dangling from the nanotube yarnshould be functionalized by passage of the yarn through ozone in achamber disposed outside of the peripheral wall 5. The ozone does notattack the length of a well-formed nanotube, but defective structuressuch as graphite are oxidized. Thus the nanotube yarn produced is cleanof impurities.

Doping of Nanotubes

The structure of a nanotube is a regular lattice that can be altered atspecific points and still maintain most of its strength. Other atoms canbe embedded in the lattice, or captured inside the tube. Specialsequences of these atoms in the nanotubes can act as diodes or otherelectronic components. Other sequences of atoms in a nanotube can beused to store information. An analogy is the strand of information thatis the DNA molecule, but in this case the molecule is not expected toduplicate, and can contain a more complex sequence of elements.

Nitrogen-doped carbon nanotubes have been discovered to have excellentoxygen reduction properties, making them suitable substitutes forplatinum in fuel cells. Nitrogen-doped carbon nanotubes could beproduced by the simultaneous electrolysis of nitrogen and a carbonaceousgas such as carbon monoxide.

Products of decomposition of other constituents, such as sulfur ionsfrom decomposition of SO₂, can also be dopants. Sulfur atomsincorporated into nanotubes would provide means for linking nanotubestogether, as with rubber, into a durable macrostructure. Sulfur dioxideis a troublesome trace pollutant in carbon dioxide from coal emissions,so simultaneous electrolytic decomposition of CO₂ and SO₂ would save anexpensive scrubbing step and would produce a valuable material fromwaste.

The present invention provides means for precisely doping long nanotubesas well as doping them by simultaneous bulk decomposition as mentionedabove in the case of CO₂ and SO₂. Because the location of the evolvingend is controllable, dopant sources, such as heated wires, can be placednear the evolving end. One useful material which might be produced bysuch means would be silver-doped carbon nanotubes, which would be strongand bactericidal as well.

As shown in FIG. 2, the introduction of dopant atoms into the evolvingnanotube end may be done through precisely controlled heated wires 40,with the dopant atoms coming off by sublimation due to heating suppliedaccording to a control for the dopant source 42. Since these ends arecharged as anodes, they do not tend to attract carbon ions. By makinguse of a known rate of growth of the main tube or tubes, doping atprecise intervals leads to increasing value in the finished nanotubecable. The dopant atoms 44 are introduced into the core vortex, whichtakes then into the formation zone 36 where they become part of thenanotube structure 46. To stop the dopants from being added further tothe structure, a dopant exhaust vent 48 is used to exhaust the gas inthe formation zone containing the dopant atoms 50. In this way thedopants can be turned on and off, or different dopants may be added insequence.

Because of the counter-rotation of the disk impellers, the radialvortices tend to be relatively stable radial spokes. But if internalconditions cause the vortices to wobble in their position as they impactthe peripheral wall, then pressure vents 21 in the reflector surface canstabilize and center the location of the vortex in the curved reflector,for better reflection of the carbon ions into the formation zone.Negative pressure 52 tends to suck the carbon ion vortex in thatdirection, while positive pressure 54 creates a pressure ridge that willpush the vortex away. The shape of the vents may be elongated to createthe effect of a circular pressure ridge or trough within the vortexreflector. Measurement of the gases coming out of the shear reactorthrough these vents can indicate the density of carbon ions inside, theamount of carbon dioxide and carbon monoxide from the oxidation ofcarbon deposits by ozone, and the level of dopant ions.

FIG. 3 shows a front view of the peripheral wall 5 seen from the space 7within the reactor, showing a vortex reflector 20 and the approximateoutline of the central conical protrusion 22 with the central opening 26for the evolving end 24. The outer ion vortex 32 and rebound vortex 38are shown, based on the motion of the upper disk impeller 2 and thelower disk impeller 4. The exhaust vents 17 are primarily used toexhaust the non-carbon ion components and carbon dust, and the reflectorpressure vents 21 control the position of the vortex as it impacts thereflector. A dopant source 40 ions is shown, as well as dopant exhaustvents 48.

FIG. 4 is an top view of the multiple radial spoke vortices between thecounter-rotating disks. Each spoke vertex represents a formation zone,so many nanotube cables 56 can be formed at once according to thepresent invention. Each of the cables can be drawn out from theperiphery and wound onto a takeup reel 58. The multitude of radialcarbon nanotube cables can then easily be bundled into nanostring oreven nanocable, materials which would have extremely good conductivityat high temperature and also very high tensile strength.

FIG. 5 shows an embodiment comprising convergent anodes. The peripheralwall 5 is the convergent portions of the anodes 2,4. The anodes in thisexample are narrowed first by a disk pinch section 62 and at theirperiphery are separated by a narrow slit opening 64. Beyond this openingis an ozone chamber 66 to clean up and functionalize the emergingnanotubes, which may emerge as nanotube yarn 68, charged by chargingmeans 12 as a cathode at the evolving end 24. The parallel currentscause the conductors to attract, so the parallel currents in themultitude of nanotubes coming out of the shear reactor would cause themto draw together into nanoyarn and stick together by van der Waalsforces. The growing nanotube yarn 68 is and withdrawn from the reactorby precision extraction means 70 and eventually wound onto the takeupreel 58.

The present invention for the vortex synthesis of nanotubes can beapplied to any material or compound which lends itself to this kind ofself assembly, in addition to the materials mentioned above.Temperature, carrier gas, electrolysis and cathode charge can be variedas needed, and the components of the shear reactor itself can featurecoatings with catalysts or manufactured surfaces to improve electrolysisor prevent unwanted buildup of coatings.

It will be evident to artisans that features and details given above areexemplary only. Except where expressly indicated, it should beunderstood that none of the given details is essential; each isgenerally susceptible to variation, or omission. It should be apparentto those of ordinary skill what particular applications of the novelideas presented here may be made given the description of theembodiments. Therefore, it is not intended that the scope of theinvention be limited to the specific embodiments described, which aremerely illustrative of the present invention and not intended to havethe effect of limiting the scope of the claims.

Instructed hindsight on the part of those of more than ordinary skill inthe particular art of desalination should not be admitted as ex postfacto evidence that the present invention was obvious or that they couldeasily have done it had they bothered, when the problem of massproduction of nanotubes with extended length and variable compositionhas remained unsolved for so long.

1. A shear reactor for the continuous synthesis of nanotubes, comprisingcounter-rotatable spaced-apart coaxial impeller/electrodes definingbetween them a space, the space comprising a shear layer when said diskimpeller/electrodes are in counter-rotation; means for counter-rotationconnected to said impeller/electrodes; means for charging saidimpeller/electrodes as anodes, said anode charging means electricallyconnected to said impeller/electrodes; a peripheral wall enclosing saidspace, the peripheral wall comprising at least one opening therethrough,the opening providing means for communicating with said space fromoutside the peripheral wall; means for feeding a source gas into saidspace at approximately the axis of rotation of the diskimpeller/electrodes, the source gas comprising cations for deposition onevolving nanotube ends within the space; means for extracting nanotubesfrom the space, said extracting means disposed outside of the peripheralwall, and said extracting means connected to nanotubes evolving in thespace; and means for charging said evolving ends of nanotubes ascathodes protruding into the space.
 2. The shear reactor of claim 1,wherein the source gas comprises cations created in an external reactor.3. The shear reactor of claim 1, wherein the source gas comprises acarbonaceous gas.
 4. The shear reactor of claim 1, wherein the sourcegas comprises vapor.
 5. The shear reactor of claim 1, wherein the sourcegas provides dopant ions.
 6. The shear reactor of claim 1, wherein saiddisk impeller/electrodes comprise openings therethrough, said openingsproviding means for gas to exit the space.
 7. The shear reactor of claim1, wherein the opening at the periphery is a gap between narrowly-spaceddisk impeller/electrodes and the peripheral wall comprises theconvergent surfaces of said disk impeller/electrodes.
 8. The shearreactor of claim 1, wherein said means for extracting nanotubes includesan exposure of said nanotubes to ozone.
 9. The shear reactor of claim 1,wherein the peripheral wall is a static shrouding wall comprising atleast one opening therethrough for the extraction of nanotubes from thespace.
 10. The shear reactor of claim 9, wherein the peripheral wallcomprises at least one concave vortex reflector centered on saidopening.
 11. The shear reactor of claim 10, wherein said opening isthrough a conical protrusion extending from the center of said vortexreflector into the space.
 12. The shear reactor of claim 1, furthercomprising means for doping evolving nanotubes by dopants introduced inthe vicinity of the periphery.
 13. The shear reactor of claim 1, furthercomprising means for maintaining evolving ends of nanotubes at a certaindistance from the peripheral wall and within a formation zone within thespace.
 14. The shear reactor of claim 13, wherein said maintaining meanscomprise a stepper motor connected to a takeup reel.
 15. The shearreactor of claim 14, wherein said maintaining means comprise sensingmeans connected to said stepper motor for changing the motor speed inresponse to the position of the evolving end.
 16. A method forpreferential synthesis of conductive nanotubes, comprising thesimultaneous steps of creating a vortex of cations in a formation zonebetween counter-rotating anodes; charging a nanotube stub as a cathode,the stub being disposed in the formation zone; and withdrawing thenanotube stub away from the anode axis so as to maintain the evolvingend of the nanotube within the formation zone.
 17. The method of claim16, further comprising the simultaneous step of controlling the speed ofwithdrawal by sensing means.
 18. Apparatus for producing dopednanotubes, comprising counter-rotatable spaced-apart coaxialimpeller/electrodes defining between them a space, the space comprisinga shear layer when said disk impeller/electrodes are incounter-rotation; means for counter-rotation connected to saidimpeller/electrodes; means for charging said impeller/electrodes asanodes, said anode charging means electrically connected to saidimpeller/electrodes; a peripheral wall enclosing said space, theperipheral wall comprising at least one opening therethrough, theopening providing means for communicating with said space from outsidethe peripheral wall; means for feeding a source gas into said space atapproximately the axis of rotation of the disk impeller/electrodes, thesource gas providing cations for deposition on an evolving nanotube end;means for extracting nanotubes from the space, said extracting meansdisposed outside of the peripheral wall, and said extracting meansconnected to nanotubes evolving in the space; and means for chargingsaid evolving ends of nanotubes as cathodes protruding into the space.19. The apparatus of claim 18, wherein dopants are not present in thesource gas, but are introduced into the space in the immediate vicinityof said evolving nanotube end.
 20. The apparatus of claim 19, whereindopants are extracted from said space in the immediate vicinity of saidevolving end to prevent their deposition on said evolving nanotube end.